Summary:
anchor the layouts of config dialogs to left
this way they will look the same normally (they
are positioned at x 0 normally) but will be
anchored to right instead if layout mirroring is enabled
CCBUG:372721
Test Plan: opened all config dialogs both in ltr and ltr layouts
Reviewers: #plasma, davidedmundson
Reviewed By: #plasma, davidedmundson
Subscribers: plasma-devel
Tags: #plasma
Differential Revision: https://phabricator.kde.org/D3456